Turns out the poor guy had been knocked off by a car (which didn't stop). He was a right mess - shirt & trousers destroyed, helmet broken etc. Bleeding pretty bad on his legs and arms. He was not walking around but just standing there.
In the prang his glasses had gone flying. Like me - he's blind as a bat without them. Couldn't even call his wife on the iPhone because he couldn't see the screen. After a bit of hunting Tyler found the glasses - unbroken fortunately. He then called his wife who came to pick him up. Poor guy was really shaken and in shock. We waited around for a while but he assured us he was fine.
After seeing this I started thinking (for a change

What's the general thought on this? Are glasses likely to come adrift from within the helmet? If mine came off they probably contact the visor - but would they become dangerous in that situation? Any thought's from the more experienced?